Re: [pkix] reminder

[Paul Hoffman <[e-mail]>]

On Aug 3, 2012, at 6:16 PM, Scott Schmit wrote:

> On Thu, Aug 02, 2012 at 01:06:43PM -0400, Stephen Kent wrote:
>> Below is the text that was briefed in the PKIX meeting yesterday and
>> that represents the current, proposed text for addition to Section
>> 3.2. Russ noted that we need to add a reference to the 2008 version of
>> X.509 from which we have cited text.  Peter will reissue the doc with
>> this change. I plan to forward that version to the IESG a week after
>> it is posted, unless we hear otherwise.
>> 
>> Steve
>> -----
>> 
>> Add the following paragraph to the end of RFC 5280, Section 3.2:
>> 
>> Consistent with Section 3.4.61 of X.509 (11/2008) we note that use
>> of self-issued certificates and self-signed certificates issued by
>> other than CAs are outside the scope of this specification. Thus,
>> for example, a web server or client might generate a self-signed
>> certificate to identify itself. These certificates, and how a
>> relying party uses them to authenticate asserted identities, are
>> both outside the scope of RFC 5280.
> 
> As I read it, if you aren't a CA and generate a self-signed certificate,
> then that certificate isn't a PKIX certificate.  Is that statement
> right?

Partially. Those certificates are outside the scope of PKIX. However...

> If so, it sort of screws up draft-ietf-dane-protocol:
> 
> From section 2.2.1:
> #     3 -- Certificate usage 3 is used to specify a certificate, or the
> #     public key of such a certificate, that MUST match the end entity
> #     certificate given by the server in TLS.  This certificate usage is
> #     sometimes referred to as "domain-issued certificate" because it
> #     allows for a domain name administrator to issue certificates for a
> #     domain without involving a third-party CA.  The target certificate
> #     MUST match the TLSA record.  The difference between certificate
> #     usage 1 and certificate usage 3 is that certificate usage 1
> #     requires that the certificate pass PKIX validation, but PKIX
> #     validation is not tested for certificate usage 3.
> #
> #  The certificate usages defined in this document explicitly only apply
> #  to PKIX-formatted certificates in DER encoding [X.690].  If TLS
> #  allows other formats later, or if extensions to this RRtype are made
> #  that accept other formats for certificates, those certificates will
> #  need their own certificate usage values.
> 
> (TLSA Certificate usage 3 is intended for self-signed "PKIX"
> certificates.)

No. It is intended for PKIX-formatted certificates, which is exactly what the DANE spec says.

> Maybe the problem is that we talk about PKIX-formatted certificates vs.
> PKIX-validated certificates, but both are handled in RFC 5280.

Can you say why that's a problem?

> Can we distinguish the two?

Yes, easily.

--Paul Hoffman